...but I think I'd just go get a better mic if I needed more accuracy ...
I won't rehash the the SM-57 vs a decent recording mic debate here. It's really not germain to the OP who needs to know how to set up his 828mkII. Hopefully, we've helped in that matter as pretty much any microphone will give him the same grief without this knowledge.
If you're of a certain age, you learned the basics on how to set up microphones and line from Mackie ads and manuals first written in the early 1990s. Once you understand the principles, almost any piece of gear behaves. I'm a bit older but found them quite helpful in teaching others as they eliminate a lot of the guesswork in trying to navigate the space between the noise floor and clipping.
http://www.mackie.com/pdf/archive/ms1202vlz_om.pdf
The 828mkII manual doesn't discuss these issues at all. It assumes you know the basics but many don't. It only says the following on pg 11:
These two trim knobs provide approximately 42dB of gain for the lo-Z XLR mic input and 17dB for the hi-Z TRS guitar/instrument input. Both inputs have preamps, so you can plug just about anything into them: a microphone, a guitar, a synth –– but don’t plug in a +4 signal here (due to the preamps): use a rear-panel TRS input instead. Use the trim knob and the “MIC” input level meters over in the metering section to calibrate the input signal level. The meters cover both the TRS and XLR input.
As I mentioned earlier, only the maximum level is important when setting the input gain via the
Trim knob. Whether it shows up on the LED display or not at low levels doesn't mean a thing.
I won't rehash the the SM-57 vs a decent recording mic here. It's really not germain to the OP who needs to know how to set up his 828mkII. Hopefully, we've helped in that matter as pretty much any microphone will give him the same grief.
BTW, all of this assumes a USA made Shure SM-57 in good working order with a properly working cable (as opposed to a counterfeit with unknown specs).
One of the problems with these is the 150 Ohm input impedance, too low for most preamps.
This next part assumes a USA made Shure SM-57 in good working order with a properly working cable (as opposed to a counterfeit with unknown specs). Nearly all low-z Shure dynamic microphones from the 1960s on have a 150 Ohm input. This includes most of the Beta series, too, so the following article applies:
Shure SM57 Impedance Modification
A simple gizmo makes a big difference
http://www.recordingmag.com/resources/r ... l/330.html
Although the specs are not in the manual, a few sources have listed the following or variations for the various 828s:
...
XLR input is 2k Ohms.
The front panel 1/4" jack on the 828 is 220k Ohms
Rear panel line inputs are 10k Ohms
This makes the recommended resistor in the article as close as you need. Here's a link to the recommended barrel adapter. You can get it pre-wired or unwired. The resistor goes between 2 and 3.
http://www.markertek.com/product/na3fm/ ... on-adapter
I have an old Shure mixer from about 1970 or so. I probably haven't used it in 40 years. I don't remember it sounding all that good the last time I fired it up. Back then, you ordered them XLRM, XLRF, Amphenol 3 or 4F, high-z 1/4" or high-z Amp 1. I still have Shure mics with all of those plugs except XLRF.
